MedeA Application Notes for Universities

This application shows the interaction of carbon monoxide with rutile.
An answer is given to the question whether CO binds with the carbon or the oxygen molecule to the surface.

The molecular builder (Molecular Builder) is part of the MEDEA standard suite of building tools. This tutorial provides an overview of the Molecular Builder’s basic functionality.

In this application note, we show how to build the isomers ethyl alcohol and di-ethyl ether and calculate their respective heats of formation.

The surface energy of a material is defined as the energy required to create a surface (h k l) from the bulk material. Surface energies are usually given in units of J/m^2.

The correct lattice parameters of a crystalline structure are of fundamental importance for any reliable computational predictions of materials properties. This case study shows the calculation of the lattice parameters of titanium carbide, TiC.

This application note deals with positioning molecules on surfaces. As an example we will investigate the adsorption of ethyl alcohol (ethanol) on a Cu (111) surface. In doing so we will consider two possible configurations for the adsorbed molecule:
1. adsorbed ethanol
2. dehydrogenated ethanol, i.e. an ethoxygen.
Running structure relaxations using VASP produces a first estimate of the relative stability of these two systems.

This case study covers the practical use of MEDEA to calculate thermochemical functions for solids, molecules and atoms. We will use VASP and PHONON for this, but the current document focuses on the thermochemistry and not the details of the calculations.

Despite the enormous progress in experimental surface science, notably with spectroscopic
methods exploiting synchrotron radiation and scanning tunneling microscopy, computations
remain one of the most useful sources for accurate data on surface structures. In fact, quite often
it is the combination of experimental and computed results, which gives the most reliable data of
surface structures. As an example, let us apply MEDEA to the Si(001) surface. This surface is the
typical substrate in the manufacturing of semiconducting devices.

Ferromagnetism has its quantum mechanic origin in the difference of spin-up and spin-down
electron densities. It is driven by a balance between a gain in exchange energy due to larger spin-
polarization and a loss in Coulomb repulsion and kinetic energy of the electron system.

In Chromium and Chromium alloys antiferromagnetic ordering and spin-density-waves (SDW) states are at the origin of many physical properties like thermal expansion, elastic constants, and electrical resistivity among others.
This document summarizes structural and elastic properties of Chromium, computed from
first principles.

The convergence of the total electronic energy as computed with VASP is determined by two key
computational parameters, namely the number of basis functions (plane wave cutoff) and the
number of k-points (k-spacing). In addition the integration of the states near the Fermi level is
influenced by a smearing parameter.